1. Field of the Invention
The present invention relates to a radiation measurement apparatus and a radiation measurement method for measuring the indoor or outdoor radiation dose.
2. Description of the Related Art
The survey meters are widely used as means for measuring a spatial dose rate at a certain location. The survey meters detect and count the radiations incoming from the circumference by using a scintillation detector, a semiconductor detector, or the like, and obtain the spatial dose rates of the radiations in consideration of the detection efficiency. The spatial dose rate means the radiation dose per unit time (in μSv/h) in a space of interest. The radiations include gamma rays, beta rays, neutron rays, and the like.
When measurement is performed by using a survey meter, it is possible to recognize the level of the spatial dose rate at the location of the radiation measurement.
Incidentally, attention to the radiation has been increasing in recent years, and there are needs for lowering the spatial dose rate at a certain location for the purpose of improvement in work or life environment. In order to lower the spatial dose rate, it is necessary to identify one or more radiation sources which greatly affect the spatial dose rate at the location, and remove or shield the radiation source. Although the survey meters can measure the spatial dose rate, the survey meters cannot detect the incoming directions of the radiations (i.e., the survey meters cannot determine the positions of the radiation sources).
Japanese Patent Laid-Open No. 2006-201086 (hereinafter referred to as JP2006-201086A) discloses a radiation directionality detector including a composite scintillator which is formed in a cylindrical shape by combining sectorial scintillators each having a central angle of 120 degrees, and photodetectors being arranged with the composite scintillator and having light-receiving faces optically coupled to the composite scintillator.
In addition, Japanese Patent Laid-Open No. 2001-305233 (hereinafter referred to as JP2001-305233A) discloses a gamma-ray-source imaging device in which a filter transmitting only gamma rays having energy equal to or greater than a predetermined value is arranged on the front side of a gamma-ray detector in a chassis.
However, according to the technique disclosed in JP2006-201086A, in the case where radiation sources of an identical nuclide exist at multiple locations, it is impossible to accurately determine the incident directions of the radiations from the respective radiation sources.
In addition, according to the technique disclosed in JP2001-305233A, in the case where a strong radiation source exists outside the field of view of the gamma-ray-source imaging device, there is a possibility that the existence of the strong radiation source cannot be detected.